Clinically in certain populations there is a significantly higher incidence of cancer of the colon in men than in women. Cancer of the colon will be produced in eight groups of male and female mice by the subcutaneous infection of 1,2 dimethylhydrazine 2-HCl. For each sex, one group will be intact controls, a second will be castrates, a third group of castrates of each sex will receive carcinogens plus suitable doses of long acting testosterone, and the fourth group of each castrated sex will receive carcinogens with suitable doses of long acting estradiol. These treatments will be given to mice beginning at 6 weeks and 10 months of age. All significant lesions will be examined histologically. A transplantable colon cancer in C57 black/6 mice will be produced with 1,2-dimethylhydrazine 2-HCl. Tissue culture lines of mouse colon cancer will be started and the transplantable tumors and tissue culture lines will be made available from research by others in needing such materials.